1. Field of the Invention
The invention relates to a road-milling machine.
2. Description of the Prior Art
Civil engineering machines of different designs are known for underground and above-ground construction. What are used for the construction of roads are self-propelled road-building machines, which include for example known road-milling machines. Known road-milling machines have a driver's position for the driver of the machine.
Because of the relatively large dimensions of road-milling machines, the driver's position is arranged at a relatively great height above the ground. For climbing to the driver's position, road-milling machines therefore have a ladder which is arranged on one side of the frame of the machine below the driver's position. To make the climb to the driver's position easier, the ladder should reach to a point which is as close as possible to the ground. The ladder should also be spaced sufficiently far away from the frame of the machine to ensure that when the driver of the machine is climbing to the driver's position there is no danger of his coming into contact with parts of the machine which may possibly even be moving.
Basically, a ladder is disadvantageous in that it increases the width of the machine for transport. This is particularly the case when, for reasons of safety, the ladder is arranged at a sufficiently large spacing from the frame of the machine.
It is also a disadvantage that the ladder arranged on the side of the frame of the machine is a fundamental restriction on the working range of the machine. Even when the machine is kept sufficiently far away from lateral boundaries such for example as a wall or the like, there is still the further danger of the ladder colliding with obstacles which suddenly make an appearance within the working range. If this happens, the ladder may be ripped from its anchorage or even destroyed.
There are known road-milling machines in which the problem of reducing the width for transport is solved by fastening the ladder to the frame of the machine with a parallelogram linkage. The parallelogram linkage allows the ladder to be folded in against the frame of the machine, thus reducing the width for transport. It is however a disadvantage that the parallelogram linkage calls for a relatively complicated structure.
As well as this, what are also known are road-milling machines which have a foldable ladder which comprises two sub-sections which are connected together by joints. The two stiles of the bottom sub-section of the ladder are fastened to the stiles of the top sub-section of the ladder by rotary joints, thus enabling the bottom sub-section to be pivoted about an axis which extends in the direction of travel. When the ladder is folded upwards, there is no restriction on the working range of the machine, nor is there any danger of the ladder colliding with obstacles. However, when the driver of the machine is at the driver's position it is not easy for him to fold the ladder upwards, even though the bottom sub-section of the ladder could still be folded upwards without any problems from the ground. However, if the ladder is not folded upwards, there is still a risk of the ladder suffering damage against obstacles which suddenly make an appearance.